haproxy: add lua optional dependency (#22169)

Formula/haproxy.rb

@@ -13,6 +13,7 @@ class Haproxy < Formula
 
   depends_on "openssl"
   depends_on "pcre"
+  depends_on "lua" => :optional
 
   def install
     args = %w[
@@ -25,6 +26,14 @@ class Haproxy < Formula
       ADDLIB=-lcrypto
     ]
 
+    if build.with?("lua")
+      lua = Formula["lua"]
+      args << "USE_LUA=1"
+      args << "LUA_LIB=#{lua.opt_lib}"
+      args << "LUA_INC=#{lua.opt_include}"
+      args << "LUA_LD_FLAGS=-L#{lua.opt_lib}"
+    end
+
     # We build generic since the Makefile.osx doesn't appear to work
     system "make", "CC=#{ENV.cc}", "CFLAGS=#{ENV.cflags}", "LDFLAGS=#{ENV.ldflags}", *args
     man1.install "doc/haproxy.1"